CN102628962B - Seismic acquisition observation system for underground microseismic detection - Google Patents

Abstract

The invention relates to a seismic wave acquisition and observation system for underground microseismic detection. In order to solve the problem that the existing system cannot form a three-dimensional image, the system takes the wellhead as the center O and consists of multiple concentric circles to form a ring structure. The number of receiving points set can be different, and generally increases with the increase of the circumference to keep the distribution of receiving points even. The received seismic data is a ring-shaped three-dimensional structure, and the layout is relatively uniform, and the attributes of seismic waves can be displayed in three dimensions. The number of receiving points arranged on the circumference is a multiple of 2 times that of the innermost circle and is evenly distributed. It has a circular structure and a radial structure at the same time. Each ray can be used as a two-dimensional section to display the properties of seismic waves. It fully considers the effectiveness and economy of downhole microseismic detection, and the layout is simple, easy to implement, and can form a three-dimensional image. The received seismic data is a ring-shaped three-dimensional structure, and the layout is relatively uniform, and the attributes of seismic waves can be displayed in three dimensions.

Description

Seismic wave acquisition and observation system for downhole microseismic detection

technical field

The invention relates to a microseismic detection and observation system, in particular to a seismic wave acquisition and observation system for downhole microseismic detection.

technical background

In seismic exploration, in order to obtain seismic records that can systematically track the effective waves of the target layer, the mutual positions of the excitation point and the receiving point must be properly arranged and selected during field data collection. This description describes the relationship between the excitation point and the receiving point and Arrangements and positional relationships between arrangements are called observation systems.

The seismic wave acquisition and observation system for downhole microseismic detection is a relatively special observation system. Its excitation source is the microseismic generated by the fracture during reservoir fracturing, which is distributed around the well and has randomness. Moreover, the energy is weak and the signal-to-noise ratio is very low. The observation systems currently used are all radial, with the wellhead as the center and several measuring lines extending radially outward. Its advantage is that it is simple to lay out and easy to implement. The disadvantage is that the farther away from the center point, the larger the distance in the arc direction, and it cannot form a three-dimensional image.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned defects of the prior art, and provide a seismic wave acquisition and observation system capable of forming three-dimensional images for downhole microseismic detection. It is a seismic wave acquisition and observation system for detecting downhole microseisms, and it is also a method for collecting seismic waves generated during downhole fracturing.

The invention relates to a seismic wave acquisition and observation system for downhole microseismic detection, which is used for detecting seismic waves generated during fracturing in wells. The observation system takes the wellhead as the center O and is composed of multiple concentric circles to form a ring structure. The number of receiving points set on each circle can be different, and generally increases with the increase of the circumference to keep the distribution of receiving points even.

The receiving points are distributed according to the following requirements: we define the radius of the i-th concentric circle as Ri (i=1, 2, ..., max), then there are: the radius of the smallest circle is R1, and the radius of the largest circle is Rmax; The circumference of a circle is Ci=2πRi, and the radius difference between the i-th circle and the i+1-th circle DRi=R(i+1)-Ri.

It is defined that Mi receiving points are arranged on the i-th circle and distributed uniformly, and Mi=N×2 ^m (N=3, 4, 5, 6, 7, 8,...; m=0, 1, 2, 3, ...) then: the arc length DLi between the two receiving points=2πRi/Mi. Define the shortest arc length as DLmin and the longest arc length as DLmax, then: DLmin≤DLi≤DLmax.

According to the above definitions, we have given a seismic wave acquisition and observation system for detecting downhole microseisms (see Figure 1): ① It is composed of multiple concentric circles, forming a ring structure, and the radius of the i-th concentric circle is Ri (i=1, 2 , ..., max), the radius of the smallest circle is R1, and the radius of the largest circle is Rmax; 2. The distance in the radial direction of the receiving point (abbreviated as the radial distance) is DRi; 3. The distance in the circumferential direction of the receiving point (abbreviated as the arc distance) is DLi, And there is DLmin≤DLi≤DLmax. ④ Arrange Mi receiving points on the i-th circle and distribute them uniformly, and Mi=N×2 ^m (N=3, 4, 5, 6, 7, 8, ...; m = 0, 1, 2, 3, ... ).

The invention fully considers the effectiveness and economy of downhole microseismic detection, and is simple in layout and easy to realize. It can form a three-dimensional image, and the received seismic data is in a ring-shaped three-dimensional structure, and the layout is relatively uniform, and the attributes of seismic waves can be displayed in three dimensions. .

As an optimization, the received seismic data is in a circle structure, and each circle can be used as a two-dimensional section to display the properties of seismic waves.

As an optimization, since it is defined that the number of receiving points arranged on the circumference is a multiple of the innermost circle (except the innermost circle) and is uniformly distributed, it has a radial structure while having a circular structure, and each ray can be used as a A 2D section showing the properties of seismic waves.

As an optimization, the distance in the radial direction of the receiving point (abbreviated as the radial distance) DRi can be constant, but the distance in the circumferential direction of the receiving point (referred to as the arc distance) DLi cannot be constant, and can only be limited within a certain range, and DLmin≤ DLi≤DLmax.

As an optimization, the seismic wave acquisition and observation system for detecting downhole microseisms of the present invention is an ideal regular observation system. In practical application in the field, due to the constraints of surface geological conditions and surface environmental conditions, reasonable Adjustment.

As an optimization, the above-mentioned system is a regular observation system under ideal conditions. In practical application in the field, due to the constraints of surface geological conditions and surface environmental conditions, it can be irregular, that is, both the radial distance DRi and the arc distance DLi can be within change within a certain range. There are DRmin≤DRi≤DRmax; DLmin≤DLi≤DLmax, where DRmin and DRmax are the minimum and maximum radial distances allowed, and DLmin and DLmax are the minimum and maximum arc distances allowed respectively.

The seismic wave acquisition and observation system for underground microseismic detection in the present invention fully considers the effectiveness and economy of downhole microseismic detection, and is simple in layout, easy to implement, and can form three-dimensional images. The received seismic data is a ring-shaped three-dimensional structure, and the layout is relatively uniform , can display the attributes of seismic waves in three dimensions.

Description of drawings

Fig. 1 is a schematic diagram of the seismic wave acquisition and observation system for downhole microseismic detection of the present invention.

Detailed ways

As shown in the figure, the present invention is a seismic wave acquisition and observation system for downhole microseismic detection, which is used to detect seismic waves generated during fracturing in a well. The observation system takes the wellhead as the center O and is composed of multiple concentric circles to form a ring structure. The number of receiving points set on each circle can be different, and generally increases with the increase of the circumference to keep the distribution of receiving points even.

We define that the radius of the i-th concentric circle is Ri (i=1, 2, ..., max), then have: the radius of the smallest circle is R1, the radius of the largest circle is Rmax; the circumference of the i-th circle is Ci= 2πRi, the radius difference between the i-th circle and the i+1-th circle DRi=R(i+1)-Ri.

It is defined that Mi receiving points are arranged on the i-th circle and distributed uniformly, and Mi=N×2 ^m (N=3, 4, 5, 6, 7, 8,...; m=0, 1, 2, 3, ...) then: the arc length DLi between the two receiving points=2πRi/Mi. Define the shortest arc length as DLmin and the longest arc length as DLmax, then: DLmin≤DLi≤DLmax.

According to the above definitions, we have given a seismic wave acquisition and observation system for detecting downhole microseisms (see Figure 1): ① It is composed of multiple concentric circles, forming a ring structure, and the radius of the i-th concentric circle is Ri (i=1, 2 , ..., max), the radius of the smallest circle is R1, and the radius of the largest circle is Rmax; 2. The distance in the radial direction of the receiving point (abbreviated as the radial distance) is DRi; 3. The distance in the circumferential direction of the receiving point (abbreviated as the arc distance) is DLi, And there is DLmin≤DLi≤DLmax. ④ Arrange Mi receiving points on the i-th circle and distribute them uniformly, and Mi=N×2 ^m (N=3, 4, 5, 6, 7, 8, ...; m = 0, 1, 2, 3, ... ).

The seismic data received by the seismic wave acquisition and observation system of the present invention has a ring-shaped three-dimensional structure, and the layout is relatively uniform, so that the attributes of the seismic wave can be displayed in three dimensions.

The seismic data received by the seismic wave acquisition and observation system of the present invention has a ring structure, and each circle can be used as a two-dimensional section to display the attributes of the seismic wave.

The seismic wave acquisition and observation system of the present invention defines that the number of receiving points arranged on the circumference is a multiple of 2 of the innermost circle (except the innermost circle) and is evenly distributed, while having a circular structure, it has a radial structure, and each Rays display seismic wave properties as a 2D section.

The radial distance (abbreviated as radial distance) DRi of the seismic wave acquisition and observation system of the present invention at the receiving point can be constant, but the distance in the circumferential direction of the receiving point (abbreviated as the arc distance) DLi can not be constant, and can only be limited within a certain range, and There is DLmin≤DLi≤DLmax.

The seismic wave acquisition and observation system of the present invention is a regular observation system under ideal conditions. When it is actually used in the field, due to the constraints of surface geological conditions and surface environmental conditions, reasonable adjustments can be made according to actual conditions.

The seismic wave acquisition and observation system of the present invention is a regular observation system under ideal conditions. When it is actually used in the field, due to the constraints of surface geological conditions and surface environmental conditions, it can be irregular, that is, both the radial distance DRi and the arc distance DLi can be change within a certain range. There are DRmin≤DRi≤DRmax; DLmin≤DLi≤DLmax, where DRmin and DRmax are the minimum and maximum radial distances allowed, and DLmin and DLmax are the minimum and maximum arc distances allowed respectively.

Example:

Suppose: R1=50m; Rmax=2000m; DR=25m; DLmin=20m; DLmax=40m; N=8.

Then there are:

① The observation system is composed of 79 concentric circles, the minimum circle radius R1 is 50m, the maximum circle radius Rmax is 2000m, the minimum circumference length is 314m, and the maximum circumference length is 12560m.

②The radial distance (referred to as radial distance) DR of the receiving point is 25m;

③The distance in the circumferential direction of the receiving point (referred to as the arc distance) is DLi, and there are 20m≤DLi≤40m

④ 8 receiving points are evenly arranged on the first circle, 16 receiving points are evenly arranged on the 2nd to 3rd circle; 32 receiving points are evenly arranged on the 4th to 7th circle; 64 receiving points; 128 receiving points are evenly arranged on the 16th to 31st circle; 256 receiving points are evenly arranged on the 32nd to 64th circle; 512 receiving points are evenly arranged on the 65th to 79th circle.

⑤ There are 18,856 receiving points in the whole observation system.

The layout of each concentric circle is shown in Table 1.

Table 1: Observation system parameter table

Claims (3)

1. A seismic wave acquisition and observation system for downhole microseismic detection is characterized in that the system takes the wellhead as the center of circle O, is composed of multiple concentric circles, and forms a ring structure. The number of receiving points arranged on each circumference is different. increases to keep the receiving points evenly distributed; The received seismic data is in a circular three-dimensional structure, and the layout is uniform, which can display the properties of seismic waves in three dimensions; or the received seismic data is in a circular structure, and each circle is used as a two-dimensional section to display the properties of seismic waves; or on the circumference The number of receiving points arranged is a multiple of 2 times that of the innermost circle and is evenly distributed. While having a circular structure, it has a radial structure, and each ray is used as a two-dimensional section to display the attributes of seismic waves; The receiving points are distributed according to the following requirements: define the radius of the i-th concentric circle as Ri, i=1, 2, ..., max, then have: the radius of the smallest circle is R1, and the radius of the largest circle is Rmax; The circumference of the i circle is Ci=2πRi, the radius difference between the i circle and the i+1 circle DRi=R(i+1)-Ri; Define that Mi receiving points are arranged on the i-th circle and distributed uniformly, and Mi=N×2 ^m , N=3, 4, 5, 6, 7, 8,...; m=0, 1, 2, 3, then there is: the arc length between two receiving points DLi=2πRi/Mi; define the shortest arc length as DLmin and the longest arc length as DLmax, then: DLmin≤DLi≤DLmax; According to the above definition, the system is given: ①It is composed of multiple concentric circles, forming a ring structure, the radius of the i-th concentric circle is Ri, i=1, 2,...max, the radius of the smallest circle is R1, and the radius of the largest The radius of the circle is Rmax; ②The radius difference of the receiving point is DRi; ③The arc length of the circumferential spacing of the receiving points is DLi, and DLmin≤DLi≤DLmax; ④ Mi receiving points are arranged on the i-th circle and distributed evenly, And Mi=N×2 ^m , N=3, 4, 5, 6, 7, 8, ...; m = 0, 1, 2, 3, .... 2. The system according to claim 1, characterized in that the radius difference DRi at the receiving point is a constant, and the arc length DLi of the circumferential distance of the receiving point is not a constant, but only limited within a certain range, and DLmin≤DLi≤ DLmax. 3. The system according to claim 1, characterized in that it is a regular observation system under ideal conditions, and when it is actually used in the field, due to the constraints of surface geological conditions and surface environmental conditions, reasonable adjustments are made according to actual conditions; The rational adjustment is: in actual application in the field, due to the constraints of surface geological conditions and surface environmental conditions, the radius difference DRi of the receiving point and the arc length DLi of the circumferential distance between the receiving points can both change within a certain range, that is, DRmin ≤DRi≤DRmax; DLmin≤DLi≤DLmax, where DRmin and DRmax are the minimum and maximum radius differences allowed, and DLmin and DLmax are the arc lengths of the minimum and maximum distances allowed.